The Data Display Debugger (ddd) is a popular graphical user
interface for command-line debuggers such as gdb, dbx,
wdb, ladebug, jdb, xdb,
the Perl debugger, and the Python debugger. Besides ``usual''
front-end features such as viewing source texts, ddd has
become famous through its interactive graphical data display, where
data structures are displayed as graphs. A simple mouse click
dereferences pointers or views structure contents, updated each time
the program stops. Using ddd, you can reason about your
application by watching its data, not just by watching it execute lines
of source code.